A medical injection system, for example, to deliver a contrast agent into a patient's vascular system for medical imaging, typically includes a pressure sensor integrated into a fluid circuit of the system for the purpose of monitoring the patient's blood pressure during the imaging procedure. Because contrast media is injected at pressures that are significantly higher (e.g., up to 1200 psi) than the blood pressure being monitored (e.g., between 0 and 5 psi), the typical blood pressure-monitoring pressure sensor is protected from exposure to the high injection pressures, for example, by isolating that portion of the fluid circuit to which the pressure sensor is coupled from that portion through which the high pressure injection flows. One example of such a medical injection system, the ACIST CVi™ system, is shown in FIG. 1.
FIG. 1 is a perspective view of an exemplary medical injection system 100 wherein a first fluid reservoir 132 supplies a pressurizing unit 130 for injection of, for example, a radiopaque contrast agent, into a patient's vascular system via a fluid circuit line 118 that feeds into a patient fluid circuit line 122. FIG. 1 further illustrates a second fluid reservoir 138 from which a diluent, such as saline, is drawn by a peristaltic pump 106 through yet another fluid circuit line 128 that feeds into line 122. The fluid circuit of system 100 further includes a manifold valve 124 and associated sensor 114 to control the flow of fluids into line 122, from pressurizing unit 130, via line 118, and from line 128. When valve 124 is open to line 128 and closed to line 118, and line 122 is coupled to the patient's vascular system, for example, by a catheter connected to line 122 at a connector 120, a pressure transducer assembly 126, which is integrated into line 128, monitors the patient's blood pressure. But, when pressurizing unit 130 is activated to inject a contrast agent, valve 124 is switched to allow the relatively high pressure flow from pressurizing unit 130 into line 122, and to isolate line 128 from the high pressure flow, not only to prevent backflow into line 128, but to also protect the pressure transducer of assembly 126 from exposure to the relatively high injection pressures that could damage the pressure sensor thereof.
One example of a pressure transducer assembly that may be employed by system 100 is the LogiCal® system available from Smiths Medical International; and another example is the Meritrans® available from Merit Medical Systems, Inc. Each of the aforementioned transducer assemblies includes a relatively low cost and disposable pressure sensor (e.g., intended for use in a single medical procedure), with an operating range that is suitable for blood pressure measurements. Thus, as alluded to above, this type of sensor would be rendered inoperable for blood pressure monitoring in between multiple injections (common in a single medical imaging procedure), if exposed to the relatively high injection pressures. Although more robust pressure sensors, which are sensitive enough for blood pressure monitoring, yet are not damaged by exposure to the higher injection pressures, are available, the cost of such sensors is prohibitive for disposable/single use medical applications. Co-pending and commonly assigned U.S. patent application Ser. No. 13/586,658 (filed on Aug. 15, 2012), which is hereby incorporated by reference, discloses apparatus and methods for isolating disposable blood pressure-monitoring pressure sensors from relatively high injection pressures in a medical injection system. Yet, there is still a need for more improved means of integrating relatively low cost and low pressure-monitoring sensors into relatively high pressure environments, while providing protection against damage from the relatively high pressures.